Frost dates for Roxborough State Park, CO
At Roxborough State Park, the median last spring frost (32°F) is May 16 and the median first fall frost is Oct 1, for a typical growing season of 136 days. For a 90% chance that the last frost has passed, wait until Jun 1. Nearby ZIP codes are in USDA hardiness zone 5b.
- May 16Last spring frost (median)50% chance of 32°F after this date
- Jun 1Safer planting date10% chance of 32°F after this date
- Oct 1First fall frost (median)50% chance of 32°F by this date
- 136 daysGrowing season (median)between 32°F freezes
Last spring frost dates
The chance that the temperature drops to the threshold after each date.
| Temperature | 90% chance later | 50% chance later | 10% chance later |
|---|---|---|---|
| 36°F | May 14 | May 29 | Jun 12 |
| 32°F | May 2 | May 16 | Jun 1 |
| 28°F | Apr 20 | May 5 | May 20 |
| 24°F | Apr 5 | Apr 25 | May 10 |
First fall frost dates
The chance that the temperature has dropped to the threshold by each date.
| Temperature | 10% chance by | 50% chance by | 90% chance by |
|---|---|---|---|
| 36°F | Sep 10 | Sep 24 | Oct 5 |
| 32°F | Sep 17 | Oct 1 | Oct 15 |
| 28°F | Sep 27 | Oct 11 | Oct 26 |
| 24°F | Oct 5 | Oct 22 | Nov 6 |
Growing season length
Days between the last spring and first fall freeze, as the length reached in 9, 5 and 1 out of 10 years.
| Temperature | 9 in 10 years at least | 5 in 10 years at least | 1 in 10 years at least |
|---|---|---|---|
| 36°F | 96 days | 116 days | 135 days |
| 32°F | 115 days | 136 days | 156 days |
| 28°F | 137 days | 157 days | 176 days |
| 24°F | 156 days | 178 days | 203 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 100% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 80131 | 5b | -15 to -10°F | 7 km |
Not the official USDA Plant Hardiness Zone Map. Zones shown here are the values published in the USDA-ARS / Oregon State University PRISM Group 2023 ZIP code tables, shown unaltered. For the official interactive map, visit planthardiness.ars.usda.gov.
About this station
- NOAA station ID USC00057249, at 39.4286, -105.0703, elevation 1864 m (6,117 ft).
- Data quality: Representative (10+ years), 24 years of freeze data.
- Average days per year at or below 32°F: 165.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Strontia Springs Dam (4 km)
- Kassler (7 km)
- Castle Rock (14 km)
- Marston Fltr Plant (21 km)
- Denver Centennial Airport (25 km)
- Parker (29 km)
- Cheesman (29 km)
- Cherry Creek Dam (30 km)
Sources
- NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020, annual/seasonal normals by station (version 1.0.1), file dated June 27, 2023; documentation.
- USDA Agricultural Research Service and PRISM Group, Oregon State University, 2023 Plant Hardiness Zone Map ZIP code tables (CONUS, Alaska, Hawaii, Puerto Rico), files dated November 17, 2023. Data © PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed November 1, 2026. Official map: planthardiness.ars.usda.gov.
- U.S. Census Bureau, 2024 Gazetteer ZIP Code Tabulation Areas file, dated August 30, 2024 (ZIP centroids used to find the nearest station).
Freeze dates are 30-year probabilities, not forecasts. Check your local forecast before planting tender plants.